World’s River Deltas Sinking Due to Human Activities, Study Says

Most of the world’s major river deltas are sinking as a result of human activity, making them vulnerable to increased flooding and posing a threat to tens of millions of people, according to a new study published by the University of Colorado. In addition to rising waters caused by global climate change, dams and reservoirs are trapping sediment upstream in river systems worldwide, man-made channels are sending sediment directly to the ocean, and the extraction of groundwater and natural gas is causing increased compaction of the floodplains, according to the report, which will be published in the journal Nature Geoscience. Twenty-four of the world’s 33 major river deltas are sinking, the authors say. And in recent years, 85 percent experienced major flooding, submerging some 100,000 square miles of land. According to the report, that flooding could increase by 50 percent by century’s end if the world experiences the 18-inch sea level rise forecast by the 2007 Intergovernmental Panel on Climate Change report. “This study shows there are a host of human-induced factors that already cause deltas to sink much more rapidly than could be explained by sea level alone,” said co-author Albert Kettner, of CU-Boulder’s Institute of Arctic and Alpine Research.